Terrible Things
by kpopgeek16
Summary: High School AU. When Mikasa delivers shell-shocking news to Eren, the boy doesn't know what to do with himself. As his time with his best friend steadily shortens, will their friendship blossom into something more? Or will it be too late?
1. Prologue

Prologue

"Eren."

"Hn." He looked up at Mikasa dangling upside down overhead, legs curled around a thick tree branch. The leaves cast a latticework of shadows over her face; how her red scarf managed to stay wound about her slim neck was a mystery to him.

"You know I didn't plan for it to be this way."

Eren remained silent. Just the thought of what was going to happen to Mikasa was enough to make his stomach curl. He balled one hand into a fist, the other pulling out hanks of grass with unnecessary violence.

"They're wrong. They have to be." He mustered the words with difficulty, though his teeth were gritted so tightly together it was a miracle they even got out.

"I saw the test results, Eren." Mikasa gracefully dropped to the ground beside him. "I start treatment tomorrow."

"You said they caught it early, right?" He looked at her with wide green eyes, the eyes of a boy who was scared and afraid and desperate but refused to admit it. Mikasa wanted to reach out and touch his face, but she dared not. There were only so many things Eren was capable of handling at once before he broke.

"Yes." She took the hand that was viciously yanking at the grass between her own. "They say there's hope. So don't fear for the worst. I'm not."

"How? How can you not be scared, Mikasa?" Her hand was smooth and soft, cool against the heat of his skin. Eren wanted to freeze this moment, just him and Mikasa and the cool breeze of oncoming fall and the leaves rusting gently overhead and his hand clasped gently in her own.

She shrugged, her dark eyes never leaving his face. "I have you. With you beside me I can face anything." She said it calmly as ever, with the utmost seriousness.

Eren swallowed hard. "Have you told Armin?"

"Not yet." She leaned back against the tree trunk beside him and pulled her knees to her chest. Their shoulders barely touched, her soft grey sweater against his T-shirt. Looking at her body she was as fit as ever, but Eren could visualize it fading into weakness and waste just as clearly as she was sitting beside him.

She would die before his very eyes. And he could do absolutely nothing to stop it.

"It's not fair," he muttered, fighting back tears of rage. "This wasn't supposed to happen. How am I—how can—I don't—"

"Eren," Mikasa said softly, and put a slim finger to his lips. "It's going to be all right."

"Can you promise that?" he asked. A myriad of emotions swirled throughout his body, seared his veins with icy fire. He burned with it, yet all he could feel was a numbing coldness. His vivid green eyes stared directly into her dark ones, as desperate and beseeching as a child clinging to their father's leg, begging him to stay home from work just one day to play.

Just as he had.

And he never saw him again.

He couldn't bear to lose her too.

"Can you?" he repeated, harsher this time.

Mikasa didn't answer.


	2. Chapter 1

Chapter 1

"Eren, please come out for dinner."

"I'm not hungry," was his subdued response. He lay on his bed, one arm flung over his eyes, the other balled into a fist on his stomach. He heard his mother sigh from beyond his bedroom door, a tired sound.

"I know, Eren."

That made him sit up. After a brief moment his mother entered the room with a somber expression and sat down on the edge of his bed. Her soft, dark hair, identical to Eren's, was in its familiar ponytail over her right shoulder, and her eyes contained immeasurable sadness for the pain her son must be feeling.

"Mikasa's parents called me right after they got the results back," she murmured softly. When Eren didn't respond, she continued, "I thought life would show you differently, Eren, and I'm sorry you have to go through this. But the doctors will do everything they can for her."

"They'd better," Eren muttered. He fell onto his back again with a heavy sigh.

"She's beginning her induction chemotherapy tomorrow. I'm sure you'll want to go see her." Carla Yeager smiled at her son reassuringly and went to squeeze his hand, but he moved away and rolled over to face the wall, burying his face in the pillow. Carla laid a hand on his shoulder instead, then slowly stood went to stand in the doorway.

"Dinner will be there if you want it," she said, then left the room.

Eren gritted his teeth. How his mother expected him to eat was simply beyond him. His best friend since childhood had cancer—acute lymphoblastic leukemia, she had said. Before the diagnosis he'd noticed her becoming more and more tired; she couldn't run for very long distances anymore. Her appetite decreased, she dropped a few pounds, but otherwise she had seemed completely fine. The last thing Eren would have guessed was cancer.

And why her? Out of everyone in the entire world, why did it have to be Mikasa? She had done nothing to deserve this, _nothing_. What would happen to him if the treatment didn't work? What would happen if she got more and more sick? What would happen if she—

"No!" Eren seized his pillow and flung it at the wall, but it did little to satisfy the rage. He paced the room up and down, his eyes frantically searching the room for something, _anything_ to punch, to kick, to shatter, to destroy. Anything that would make this horrible ache inside go away.

He stood up, hands straight down by his sides and balled into fists. Crossing the room to his desk with quick strides he snatched his heavy calculus book from the tabletop. His knuckles whitened as his grip grew fiercer, the vise of his fingers growing so tight that his whole frame shook with pent-up fear, indignation, anguish, and directionless fury. He snapped his head to the side, doing a short, quick, violent turn and releasing the book with an almost thoughtless flick of his wrists. And then: a whoosh of an impressive mass sailing through the air. A fluttering, flapping clatter as loose papers, stained with ink and scribbled over with limits, derivatives, L'Hopital, integrals, meaningless caricatures of his teacher's amusingly lacking stature, flew out of the now-open pages of the book like birds taking flight. A final, cacophonous THUNK as the book hit the wall, miraculously leaving it unscathed. Eren's breath hissed through his clenched teeth as he stared at the book on the ground in the sudden silence.

The heavy quiet was broken with the notes of his phone, blaring "Jiyuu no Tsubasa" from his desk. Did he really want to answer it? Not really. But he had to admit, talking to someone may help. He picked up the phone and checked the caller, then pressed it to his ear and dully said, "Hello."

"Hey, Eren." The voice that answered him was equally dejected.

"Armin." Eren moistened his lips before speaking. "Did Mikasa talk to you?"

"Yeah." Eren heard a faint sniffling noise; Armin was crying. "Are you going to go see her tomorrow?"

"Of course I am!" Eren responded with irrational anger, then immediately regretted it. The last person who needed the extra hurt was Armin. Eren heard the rasping of a sharp intake of breath over the receiver. Closing his eyes and exhaling slowly, he stumbled blindly backward until he felt his back press against the cold wall, sliding down the forest-green painted surface until his body lie in a pile on the floor, legs akimbo and head in hands. "I'm sorry, Armin. I didn't..."

"Don't worry about it, Eren." A rustling on the other end of the phone. "I understand."

Eren pinched the bridge of his nose and sighed, yet again. "It's just... I never expected it, you know? I mean, nothing's ever kept Mikasa down. Not even breaking her leg last year. She'd have run that whole track meet in crutches if Coach Hannes would've let her." He smiled ruefully.

A wry chuckle rasped from the other end of the receiver. "And she would've won," said Armin

Eren let a thin, wavering laugh out at how true that statement was. "You know, for the longest time I thought she was -" and just like that, he was numb and mute and cold and paralyzed and helpless. He couldn't finish the word.

A few moments of silence passed, and then Armin spoke. "Invincible?"

Eren's eyes squeezed tightly shut until he could see white starbursts. His shoulders jumped and shook as he tried to hold his grief in.

Armin coughed softly into the phone. "I did too." A beat of silence. "She was always there for us, you know? Ever since we were little. The bigger kids would always pick on us and make fun of us, I'm sure you remember that vividly. I'd always try to talk them off, and when that didn't work you tried to fight them off..."

"And when that didn't work, Mikasa broke their noses," Eren whispered, striving desperately to keep his voice level.

"Precisely." Another beat. "And no matter what the problem, she was always there in the end to protect us. Always. We always had each other's' backs."

Disjointed images flashed through Eren's mind. Armin cowering in a corner, trying desperately to hide behind a book as faceless bullies jeered at him. Himself barreling in, all force and no finesse, to his friend's rescue, the starburst of a fist smashing into his face still fresh after years and years. And then, out of the corner of his recollections, Mikasa running silently down towards her friends, hands loose at her sides. And then the bullies were gone, and as usual Eren blustered on at their backs, punching the air in vicarious victory and still running on adrenaline.

Suddenly, more jagged fragments. Mikasa stumbling during track practice. Mikasa's portions at lunch gradually shrinking smaller and smaller. How much bonier she looked, her legs becoming less and less toned and more and more skeletal. Bruises on her arms and knuckles from boxing, bruises that shouldn't have been there. Mikasa coming into school with dark rings under her eyes, her words full of forced energy when he asked what was up. Jagged, broken, razor-sharp, lacerating images of a stalwart constant in his life crumbling to pieces, his closest friend's light darkening ever-slowly, insidiously.

How could it have crept up on him like this?

And then suddenly it wasn't the only thing that crept up on him, suddenly his throat seized up and released and a choking noise spilled out of him, sticky and caustic like sewage, like irradiated sludge that eats away at your insides and warps the blood in your veins to stone, and hot molten tears of grief and helpless anger and pain spilled over his face and hands and it all just melted away as he sobbed into the receiver.

"Why, Armin? Why her, of all people? Why is it that when she needs help, like we always do, we can't just make it vanish like she does?" And then no more words, only those desperate, choking, poisonous tears.

"Eren." His head snapped up as Armin's suddenly strong, clear, and strident voice slashed through the noxious fog of anguish. "Eren, stop talking about her like she's already gone." Eren froze.

"What did you say?" he whispered into the receiver.

"I said, stop talking about her like she's already gone." A sharp exhale, a sandpapery rasping of air over Eren's jangling psyche. "She's still here, Eren. She's in the hospital right now. And it's a betrayal of her trust and our hopes if you keep talking about her like nothing's left. There's always something we can do, always ways to fix things. And we're doing it as soon as we can. You said we're seeing her tomorrow, right? Because I am. And you know what I was about to say? I was about to say, we still have each other's' backs. Because as long as we're together, the three of us, we're invincible. Nothing can touch us, not people, not cancer, not even giant human eaters or the Ubermensch or a god." Eren let out a high-pitched noise that could've been a chuckle or a sob. Fiction, philosophy, and mythology all in one boastful declaration. Ever the bookworm, that Armin.

"So don't keep talking like that, Eren. Where's the determination to succeed that I know, that Mikasa knows? That spirit, that fiery oath to conquer everything in your path and succeed no matter what?" Eren's shoulders stilled slowly. "What you can do for Mikasa right now, at this very moment, is stay true to that spirit. And fight for her."

Eren didn't say anything for a long time. He sat and stared dully at the interlocking fibers of the carpet in front of him. Three strands had knotted themselves into a tight connection right under his gaze. And then, finally, his eyebrows shot together and his fists clenched and his eyes shone once again. "Fight on. Fight on for Mikasa. Never stop fighting. I swear I'll never stop fighting." Armin was right. He'd continue to fight on, no matter what.

* * *

**AN: Thanks to my boyfriend for helping me with this chapter. ^^**


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